Composite body of magnesium and steel, and method of making same



United ate Pate O COMPOSITE BODY OF MAGNESIUM AND STEEL, AND METHOD OFMAKING SAME Jerome J. Kanter, Palos Park, and Alvin F. Lahr and -EdwardV. Havel, Chicago, 111., assignors to Crane Co., Chicago, 111., acorporation of Illinois No Drawing. Application January 4, 1956 SerialNo. 557,244

8 Claims. (Cl. 29-4975) cleaned by buffing .with a wire The ferrous cladmagnesium article of manufacture of I this invention may be prepared bybonding the magnesium in the solid state.

There has been much work done in the cladding of aluminum to steel.However, the problems of bonding magnesium to steel are quite different.There is a great deal of activity between aluminum and steel and theprincipal problem in the past has been to reduce or limit this activity.On the other hand, in the case of magnesium, there is only limitedchemical affinity to steel so that the problem is not in reducing orlimiting their activity, but to encourage it. In this connection, it isinteresting to note that at present there is no available equilibriumdiagram for magnesium iron although there is one for aluminum iron.

It is, therefore, an object of this invention to provide a bond betweenmagnesium and steel or iron that will not come apart upon deformation.

It is a further object of the invention to provide a method for claddingmagnesium in its solid state to ferrous articles. 7

To the accomplishment of the foregoing and related ends, said inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description setting forth indetail certain illustrative embodiments of the invention, these beingindicative, however, of but a few of the various ways in which theprinciple of the invention may be employed.

Broadly stated, this invention relates to a method of cladding magnesiumto ferrous articles that includes the step of providing the ferrousarticles with a coating of metal soluble in magnesium, and urging themagnesium and ferrous articles together under an atmosphere of a noblegas.

In carrying out the method, if the surface of the ferrous article to becoated is not already substantially free from foreign matter, it may becleaned in any suitable manner such as by pickling, wire brushing, orsand blasting. Pickling is the preferred form and may be accomplished bya dipping in a 15% aqueous solution of hydrochloric acid, although otherways are known which may be used.

The cleaned ferrous metal surface is then plated or coated with a thincoat of metal soluble in magnesium, such as copper, nickel, tin, zinc,aluminum, beryllium, cadmium, cobalt, lead, silicon, or silver, byanelectroplating step or other suitable coating operation. This coatingprovides an area of increased solubility with respect to the magnesiumwhereby the ferrous base is left clean to form a bond with the magnesiumby virtue of the solution activity of said coating.

The thickness of the coating metal on the ferrous am;

cle may range from 0.0001 inch to 0.0010 inch, although about 0.0002inch is the usual thickness ordinarily employed.

The magnesium article or material may be commercial grades of magnesiumor a magnesium base alloy.

The magnesium is cleaned by dipping it in muriatic acid, washing withwater, and air, drying. .The surface of the magnesium may be scratchedwith a wire brush after drying. Alternatively, the magnesium may bewheel and blowing-off the fine particles with air.

In carrying out the method, the ferrousmetal article, having a thin coatof copper, nickel, tin, zinc, aluminum, beryllium, cadmium, cobalt,lead, fsilicon, or silver is placed'against the magnesium with thesurface of the ferrous article having the coating metal contacting themagnesium. Ordinarily, the materials are then heated to an elevatedtemperature, below the melting point of the magnesium, under anatmosphere of a noble gas. I At the same time the magnesium and ferrousarticles are urged together so as to achieve solid surface bonding atthe interface. 7

It is critical to the present invention that the heating and bondingtake place under the atmosphere of a noble gas. The noble gases includehelium, neon, argon, crypton, zenon, or mixtures of the foregoing.

The temperature must be sufiiciently high to cause the coating metal todiffuse into the magnesium, ordinarily just below the melting point ofthe magnesium article. The temperature must be below the melting pointof the magnesium material for bonding in the solid state. Usually thetemperatures will range from about 600 F. up to about 1200 F. Incarrying out the bonding the ferrous metal article and magnesium may beclamped together under pressure and placed in a chamber containing anoble gas. The chamber is then heated to the proper elevatedtemperature. The assembly is then allowed to cool in an atmosphere of anoble gas.

The process may also be carried out continuously in which case theferrous article and magnesium are passed between a pair of rollers whichurge them together under an atmosphere of a noble gas at elevatedtemperatures.

If magnesium alloys are used, the temperature will normally be lowerthan that for pure magnesium. The primary requisite is to raise thetemperature to an amount sufiicient for the coating metal to diffuseinto the magnesium material without melting the magnesium material.Inany case, the melting point of the magnesium is the upper temperaturelimit for the process.

The following example is given by way of illustration of the process andshould not be construed in any way as'limiting the present invention,except as defined by the appended claims.

Example A sheet of steel was cleaned by degreasing with trichlorethylenefollowed by a mild alkaline anodic and cathodic cleaning with a waterrinse, a 60 Baum sulphuric acid cleaning with a water rinse followed bycopper plating for ten minutes at 20 amperes per square foot in a coppercyanide solution to a coating of 0.0002 inch of copper. The coppercoated steel sheet was then rinsed in water and dried.

A sheet of magnesium was cleaned by dipping in hydrochloric acid,washing under water, and drying in air. The surface was scratched with awire brush.

The magnesium sheet was placed against the surface of the steel sheethaving the coating of copper, and the two sheets urged together with aslight amount of pressure with a C-clamp. This assembly was then placedin a chamber which was provided with an atmosphere of Patented Nov. 10,1959 an inert gas and then heated to about 1100 F. The article formed bythis process of the invention does not come apart at the bond whendeformed. A micrograph of the bond showed that a eutectic compound hadbeen formedat the inner surface .by difiusion of the coating metal intothe magnesium.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed. p

' We therefore particularly point out and distinctly claim as. ourinvention:

1. The method of bonding ferrous articles to mag nesium or magnesiumbase alloy articles in the solid state which comprises: j

(4) Providing the ferrous article with a thin surface ofa coating metalwhich is soluble in magnesium;

(b) Placing a solid article of magnesium' material against the surfaceof said ferrous article having said coating metal;

(0) Heating said assembly to a temperature sufficient to cause thecoating metal to diffuse into the magnesium under an atmosphere of anoble gas and below'the melting point of said magnesium material; and

(d) Urging said magnesium article and said ferrous article together soas to achieve solid phase bonding at the interface.

2. The method of claim 1 wherein said coating metal is nickel.

3. The method of claim l 'wherein said coating metal is copper.

4. The method of claim 1 wherein said coating metal is silver.

5. The method of claim 1 he e n sa d coating m tal is cadmium.

6. The method of claim 1 wherein said coating metal is aluminum.

7. The method of claim .1 wherein said. argon.

8. The method of claim 1, wherein said, noble g s is helium. t

noble gas is References Cited in the file of this patent UNITED STATESPATENTS Si g l ct- 2.3, .1956

1. THE METHOD OF BONDING FERROUS ARTICLES TO MAGNESIUM OR MAGNESIUM BASEALLOY ARTICLES IN THE SOLID STATE WHICH COMPRISES: (A) PROVIDING THEFERROUS ARTICLE WITH A THIN SURFACE OF A COATING METAL WHICH IS SOLUBLEIN MAGNESIUM; (B) PLACING A SOLID ARTICLE OF MAGENSIUM MATERIAL AGAINSTTHE SURFACE OF SAID FERROUS ARTICLE HAVING SAID COATING METAL; (C)HEATING SAID ASSEMBLY TO A TEMPERATURE SUFFICIENT TO CAUSE THE COATINGMETAL TO DIFFUSE INTO THE MAGNESIUM UNDER AN ATMOSPHERE OF A NOBLE GASAND BELOW THE MELTING POINT OF SAID MAGNESIUM MATERIAL; AND (D) URGINGSAID MAGNESIUM ARTICLE AND SAID FERROUS ARTICLE TOGETHER SO AS TOACHIEVE SOLID PHASE BONDING AT THE INTERFACE.